<p>Both expo laptops Clowley and Aziraphale use DHCP over wifi to get an IP4 address and the identity of a DNS nameserver. Neither laptop has any other configuration.
<p>If you connect your laptop or phone to the Potato hut wifi you will connect in the same way.
<h3>The Gasthof Wifi</h3>
<p>The Gasthof WiFi - which you can use if you are close enough - is "StaudnGast" and has no WiFi password but there is a login webpage. It allocates IP addresses in the range 192.168.2.x etc. The antenna is now on the first-floor balcony within sight of the tatty hut window. You can get the password from the Gasthof front desk, or during expo it is usally written on the whiteboard in the potato hut. In the scripts published in this handbook we use the word GASTSECRET instead of the real password.
<p>If you are not actively using the internet, the Gasthof system will close the connection and you will have to re-login again, typing the password into the login page.
<h3>The Potato hut Wifi</h3>
<p>The potato hut WiFi has <ahref="https://www.howtogeek.com/334935/what-is-an-ssid-or-service-set-identifier/">SSID</a> "tattyhut" with our usual cavey:beery password. Like almost every other wifi anywhere it is running DHCP and allocating IP addresses to your device.
<p>The DHCP system is issuing IP4 addresses of the form 192.168.1.x where x is a number between 11 and 199 with a lifetime of 48 hours.
<p>The <em>Expo laptops</em> acquire a dynamic local address of this form, as does any other laptop or phone connecting to this wifi.
<h3>How it works - in words</h3>
<p>The <ahref="https://en.wikipedia.org/wiki/Acer_Aspire_One">Acer Aspire One</a> netbook is running Debian Linux operating system with the lightweight <ahref="https://xfce.org/">[xfce]</a> window mananger. It runs a script once every 60s which checks whether it can access the internet. If it can't, it attempts a re-login to the Gasthof wifi system, which takes 5-10 seconds. If it still can't access the internet it deletes nearly all the configuration and reloads everything - which takes about 30s.
<p>Because of a permissions difficulty, the scripts on the netbook live in <var>/root/fakenet</var> so that the cron job (running as root) can access them. [This is not the usual Linux place to keep such things.] The cron file lives in the usual place in <var>/etc/cron/cron.d/fakenet</var>.
<p>The Acer Aspire One ("tclaspire3") is on a static address <ahref="http://192.168.1.100/">192.168.1.100</a> on WiFi but <ahref="http://192.168.200.100/">192.168.200.100</a> on the ethernet cable.
This is the address to use for configuring it using ssh when everything else has failed. So to manage the
This used to need running once or twice a day when the internet stops working, but it was radically fettled in 2022 and so should be much more reliable.
Sometimes you may have to walk over to the blue Acer Aspire netbook and run this script directly by typing on its keyboard
as the network has collapsed so badly that <spanstyle="font-family:monospace">ssh</span> doesn't work.
<p>In 2017 we arrived on expo to discover that our hard-drive in the hut had died (taking the music collection with it) which triggered the general reconfiguration to connect the tattyhut to
the internet continuously and not to have our own local server. This coincided with a much-improved WiFi service at
the Gasthof. We continued with the wifi service in the hut but now it also connects to the external internet instead of to a 'pretend' internet (which is why the system is called 'fakenet').
<p>In 2022 Wifi reception from the Gasthof was very poor. The connection script was improved so that dropped connections were restored more quickly. However the basic bandwidth with a cheap antenna was not enough.
<p>In 2023 a new Wifi device (the Alfa) should restore decent connectivity. We hope this will improve everything to how it was in 2019. However this Alfa has proved to be a right bastard to find the right drivers for. Wookey has had to be inventive in using an Ubuntu PPA to make it work with the Acer Aspire 1.
<p>Also during winter 2023/23 Wookey upgraded the operating system on the Acer Aspire 1 netbook from whatever Linpus ancient Debian it had been running to a decently almost-modern Debian distribution. This required much coaxing. As of 26 March, it is still a couple of Debian versions behind where we would want it to be.
<p>The structure of the system was created by Wookey in 2013 who used the fakenet principle and the netbook to run training sessions for the Cave Survey Group in the UK. [This is why the script has an extra level of parameter setting that might seem necessary: it has 'csg' and 'expo' options, but the two configurations have diverged so much over the years that this is merely a fossil.]
<p>The part of the script that logs into the Gasthof wifi was written by Mark Shinwell in 2017 and re-edited by Sam Wenham in 2019. Wookey made it more robust on expo in 2022.
